Phylocode, Cladistics and Eclecticism ...

[Thomas DiBenedetto]

-----Original Message-----
From: Ken Kinman
     I'm talking about *real* apomorphies, the ones that cause the
divergence (speciation) to occur.
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Apomorphies that affect the ability to interbreed are not the only events
that can cause speciation. Speciation is the general event of lineage
divergence. This can occur through geographic isolation as well as
apomorphic change. Gondwanan freshwater fish populations, or
terrestrially-bound animal populations could have (and almost certainly did)
find themselves  with some members on the African plate and others on the
South American plate, never to be in a position to interbreed again. The
lineage was permanently split - each new species henceforth was on its own
independent evolutionary trajectory - and it was totally irrelevant whether
or not the population halves could have interbred in theory. Your speciation
defintion is based either on an assumption that permanent vicarience events
never happen, or that such events are not the causative factor in the
divergence of the lineage. This is clearly wrong.
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Kinman:
 At least one such apomorphy must cause a
severe reduction in the ability to interbreed with members of the mother
population.  Any daughter population which lacks such an isolating apomorphy
is still able to interbreed with the mother population, so they are still
the same species.  I'm not arbitrarily stating it to be true, that's just
the way it is.
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Perhaps you have a reason for stating this (i.e. perhaps it is not
arbitrary), but that does not mean that it is "just the way it is" in the
real world. There is not a golden tablet with the objectivly true defintion
of "species" written upon it  which mandates that we consider two organisms
as being part of the same species because they could, in some totally
theoretical, abstract sense, possibly interbreed even though one of them
might be born many years after the other has died. This is an absurd and
unworkable defintion of species.
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Kinman:
 The ability of populations to interbreed is plesiomorphic.
Interbreeding can continue until a daughter population evolves a
reproductively isolating apomorphy, thus budding off as a new species.
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You are focusing your definiton on the wrong level. The causitive factors
behind lineage divergence are important, but the key issue in speciation is
the divergence itself, however it is caused.
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Kinman:
     For example a change in the chemical structure in a pheromone.  This is
caused by a mutation which only gradually spreads in a population.  The
budding population with this new character will always start out small.
That's how evolution works.
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That is how evolution works sometimes, not always. Your definitions, and
seemingly your entire approach, is dependant on a narrow model of how
evolution works. This is a problem. We need a systematics which is
insensitive to any particular evolutionary model, but can rather simply
report about the diversity that exists and the relationships that can be
inferred, irrespective of how that actually arose. Otherwise, we would
requrie a new systematic structure everytime we learn some new detail about
the evolutionary process.

Tom DiBenedetto